Seasonal transport variability of the Deep Western Boundary Current in the equatorial Atlantic
Seasonal transport variability of the Deep Western Boundary Current in the equatorial Atlantic
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DOI：
10.1029/97jc02327
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发表时间：
1997-12
影响因子：
--
通讯作者：
J. Fischer;F. Schott
中科院分区：
文献类型：
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作者：
J. Fischer;F. Schott
分析了21个北大西洋上层和中层深水区（NADW）近一年的海流计记录，确定了赤道大西洋上层深水西边界流（DWBC）的平均值和波动特征。该调查基于1989/1990、1990/1991和1992/1994三个不同部署期在44°W处的系泊阵列，并由沿沿着44°W和35°W的海流剖面进行补充。赤道以北西经44°处约100公里宽的DWBC附着在地形上，最大流速超过70 cm s−1。DWBC核心内的电流遵循地形，平均电流方向和最大方差方向之间的密切一致性表明，赤道附近的DWBC变化的主要贡献是由于脉冲，而不是蜿蜒。对于平均运输的上部和中部NADW，目前米记录平均超过其部署期间产生的最佳估计为13西弗在深度范围1000至3100米。平均运输似乎稳健，从两个不同年份的数据子集产生了大约相同的平均运输，即12.4和13.6西弗。DWBC的运输时间序列显示了明确的季节性周期，范围从9月/10月期间不到7 Sv到1月/2月期间约25 Sv。年度和半年运输谐波有类似的幅度，在约6 Sv，他们一起解释了约三分之二的总运输变异。在穿越赤道后，DWBC分裂成两个核心，主要流向沿着3.5°S附近的海山链，35°W附近。在35°W，大约1.5°S以南，输送变率的震级和相位与44°W相似。此外，对于从DWBC上部分离的NADW下部流动，在44°W的深部记录中观察到类似的周期性和相位。
A total of 21 about year-long current meter records in the depth range of the upper and middle North Atlantic Deep Water (NADW) were analyzed to determine the mean and the fluctuations of the upper Deep Western Boundary Current (DWBC) in the equatorial Atlantic. The investigation was based on moored arrays at 44°W from three different deployment periods, 1989/1990, 1990/1991 and 1992/1994, and was supplemented by current profiling along 44°W and 35°W. The approximately 100-km-wide DWBC at 44°W, just north of the equator, was attached to the topography with the current maximum exceeding 70 cm s−1. Currents within the DWBC core followed the topography, and the close agreement between the mean current direction and the direction of maximum variance indicated that the major contribution to the DWBC variability near the equator was due to pulsing rather than meandering. For mean transports of upper and middle NADW, the current meter records were averaged over their deployment duration yielding a best estimate of 13 Sv in the depth range 1000 to 3100 m. The mean transport appeared robust, as subsets of the data from two different years yielded about the same mean transport, namely, 12.4 and 13.6 Sv. The DWBC transport time series showed a definite seasonal cycle, ranging from less than 7 Sv during September/October to about 25 Sv during January/February. Annual and semiannual transport harmonics had similar amplitudes, at about 6 Sv each, and together they explained about two thirds of the total transport variability. After crossing the equator, the DWBC splits into two cores with the major flow along a chain of seamounts near 3.5°S, near 35°W. Magnitudes and phases of the transport variability at 35°W, south of approximately 1.5°S, were similar to that at 44°W. Further, for the flow of lower NADW which was detached from the upper DWBC core, similar periodicity and phases were observed in the deep records at 44°W.